Stretch removable adhesive articles are desirable for use in adhering to skin or delicate surfaces. Stretch removability occurs as a result of the selection of a stretch removable adhesive, i.e., one that has sufficient internal strength that it can be gripped and removed on its own even in the absence of a backing, or as a result of the selection of a stretch removable backing, i.e., a backing that allows a construction that includes a weaker adhesive to be removed by stretching.
Pressure sensitive adhesive tapes and the like are used in a wide variety of applications where there is a need to adhere to skin, for example, medical tapes, wound or surgical dressings, athletic tapes, surgical drapes, or tapes or tabs used in adhering medical devices such as sensors, electrodes, ostomy appliances, or the like. A concern with all these adhesive-coated products is the need to balance the objective of providing sufficiently high levels of adhesion to ensure that the pressure sensitive adhesive products do not fall off, while ensuring that the underlying skin or other delicate surface experiences a low amount of trauma, damage, pain, or irritation during use and/or removal. These goals are generally conflicting. Many approaches have been suggested to balance these conflicting goals; however, there still remains a need for products that effectively do so.
For example, film-backed, normally tacky, pressure sensitive adhesive tapes that are highly stretchy and elastic are known to be easily removed from a surface by stretching the tapes lengthwise in a direction substantially parallel to the plane of the surface. For such tapes the adhesion capability substantially disappears as the film is being stretched. If such tapes are too elastic, they may exhibit large recoil when the stretching force is removed, which can be undesirable. Additionally, highly elastic tapes tend to substantially recover their original shape when the stretching force is removed, and they are therefore not useful for indication of tampering or for guaranteeing single uses for hygienic purposes.
Such so-called “stretch release” or “stretch removable” adhesive constructions often include backings having stretchabilities that typically match those of the adhesives. Other backings of differing stretchability can be used by using a pre-reated/damaged backing having a strength that is inconsequential in the stretch removal process and an adhesive that is substantial enough to alone support the stretch removal process, i.e., a stretch removable adhesive. Although many of such constructions are useful, there is still a need for stretch removable adhesive articles, particularly those that can be easily removed from a surface such as skin or other delicate surface without a significant amount of pain, trauma, damage, or irritation.
Such stretch removable adhesive products preferably include a pressure sensitive adhesive. Pressure sensitive adhesives are generally characterized by their properties. Pressure sensitive adhesives are well known to one of ordinary skill in the art to possess properties including the following: (1) aggressive and permanent tack, (2) adherence to a substrate with no more than finger pressure, (3) sufficient ability to hold onto an adherend, and (4) sufficient cohesive strength to be removed cleanly from the adherend. Many pressure sensitive adhesives must satisfy these properties under an array of different stress and/or rate conditions. Additives may be included in the pressure sensitive adhesive to optimize such properties of the pressure sensitive adhesive. Care must be exercised in choosing additives that do not adversely affect one property (e.g., tack) while enhancing another (e.g., cohesive strength).
For certain adhesive articles, such as medical articles, it is desirable for the article to be breathable. The use of nonwoven webs of pressure sensitive adhesive fibers is one known method of accomplishing breathability. Fibers having a diameter of no greater than about 100 micrometers (microns), and particularly microfibers having a diameter of no greater than about 50 micrometers, have been developed for such uses. The fibers can be made by a variety of melt processes, including a spunbond process and a melt-blown process. In a spunbond process, fibers are extruded from a polymer melt stream through multiple banks of spinnerets onto a rapidly moving, porous belt, for example, forming an unbonded web. This unbonded web is then passed through a bonder, typically a thermal bonder, which bonds some of the fibers to neighboring fibers, thereby providing integrity to the web. In a melt-blown process, fibers are extruded from a polymer melt stream through fine orifices using high air velocity attenuation onto a rotating drum, for example, forming an autogenously bonded web. In contrast to a spunbond process, no further processing is necessary. Many melt-processed fibers, however, do not have adequate cohesive strength. This can result from the extreme conditions that can cause a breakdown of molecular weights of the polymers used to make the fibers.
What is desired is an adhesive fiber that has improved cohesive strength without losing the tackiness indicative of a pressure sensitive adhesive. In conjunction, it is desirable to create an adhesive fiber that is removable from a substrate with ease without losing the tackiness indicative of a pressure sensitive adhesive. Additionally, a pressure sensitive adhesive fiber that can be used in a stretch removable article, particularly a medical article, is desirable.